21680231 has 2 divisors, whose sum is σ = 21680232. Its totient is φ = 21680230.

The previous prime is 21680227. The next prime is 21680249. The reversal of 21680231 is 13208612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21680231 - 2² = 21680227 is a prime.

It is a super-2 number, since 2×21680231² = 940064832426722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21680197 and 21680206.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21680251) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10840115 + 10840116.

It is an arithmetic number, because the mean of its divisors is an integer number (10840116).

Almost surely, 2^21680231 is an apocalyptic number.

21680231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21680231 is an equidigital number, since it uses as much as digits as its factorization.

21680231 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21680231 is about 4656.2034964121. The cubic root of 21680231 is about 278.8397181492.

Adding to 21680231 its reverse (13208612), we get a palindrome (34888843).

The spelling of 21680231 in words is "twenty-one million, six hundred eighty thousand, two hundred thirty-one".